The relationship between the structure and the fluorescence of the benzothiazole derivatives and their metal chelates were investigated along with characteristics necessary for the fluorescence. By the chelation with zinc, N-salicylidene-4-aminobenzothiazole is held in plane and its electronic state was scarcely influenced, which induce fluorescence. In the fluorescent zinc chelates, the π electron distribution inclines towards the phenol portion from the thiazole portion in the transition from the ground state to the first excited state and the electron densities of the coordinate atoms to the central zinc ion do not almost change between both states. The fluorescence of the zinc chelates is due to π*-π transition. The effect of additional substituent groups on the fluorescence was also examined along with the correlation between the stability constant and the fluorescence intensity of the metal chelates.